Method for Modulating Navigation Signal

1. A method for modulating navigation signal, the method comprising the following steps: 1) dividing frequency of a control clock CLK 0 to obtain a pseudo-code generating drive clock CLK 1 and a time division multiplexing (TDM) control clock CLK 2 by utilizing a first frequency divider and a second frequency divider, respectively, where, a frequency of the control clock CLK 0 is four times that of a binary subcarrier, a frequency of the pseudo-code generating drive clock CLK 1 is ½ of a code rate, and a frequency of the TDM control clock CLK 2 is equivalent to the code rate; 2) driving the CLK 1 to generate pseudo-code c BD of a data channel of an upper sideband, pseudo-code c AD of a data channel of a lower sideband, and pseudo-code Cp of a pilot channel by utilizing a pseudo-code generator; driving the CLK 0 to generate a binary sine subcarrier SC B,sin and a binary cosine subcarrier SC B,cos by utilizing a subcarrier generator; 3) modulating the c AD by a lower sideband d A to generate a baseband signal component C A of the data channel of the lower sideband by utilizing a first multiplier; modulating the c BD by an upper sideband waveform d B to generate a baseband signal component C B of the data channel of the upper sideband by utilizing a fourth multiplier; 4) modulating the subcarriers, which comprising: (4.1) negating the C A and adding to the C B , and multiplying with the SC B,sin to get a signal component of data channel at Q branch by utilizing a subtracter and a second multiplier; adding the C A to the C B and multiplying with the SC B,cos to get a signal component of data channel at I branch by utilizing a second adder and a fifth multiplier; multiplying the C P by 2 and then multiplying with the SC B,cos to get a signal component of the pilot channel at I branch by utilizing a seventh multiplier and an eighth multiplier; and (4.2) when the CLK 2 is in a time slot of odd chip, allowing the signal component of the data channel at Q branch to be a signal component of a baseband signal at Q branch by utilizing a first time division multiplexer, and allowing the signal component of the data channel at I branch to be a signal component of a baseband signal at I branch by utilizing a second time division multiplexer; when CLK 2 is in a time slot of even chip, allowing zero signal to be the signal component of the baseband signal at Q branch by utilizing the first time division multiplexer, and allowing the signal component of the pilot channel at I branch to be the signal component of the baseband signal at I branch by utilizing the second time division multiplexer; and 5) modulating a sine phase carrier by the signal component of the baseband signal at Q branch, modulating a cosine phase carrier by the signal component of the baseband signal at I branch, and combining the modulation result of the two branches to obtain a modulated radio frequency signal by utilizing an RF modulator.

2. The method of claim 1 , wherein in step ( 4 ), corresponding baseband signal components at Q branch and I branch are looked up in a modulation mapping table according to the current C A , C B , and C p value by utilizing a baseband modulation module; a method to establish the modulation mapping table comprises: combining all possible C A , C B and C p values and processing each combination thereof according to steps (4.1)-(4.2) to get the baseband signal component at Q branch and I branch corresponding to each combination, and recording each combination and corresponding Q branch component and I branch component thereof in the baseband modulation module to establish the modulation mapping table.

3. A system for modulating navigation signal according the method of claim 1 , the system comprising: a) a first multiplier ( 3 ), a first subtracter ( 4 ), a second multiplier ( 7 ), and a first time division multiplexer ( 11 ), which are connected in order; b) a fourth multiplier ( 2 ), a second adder ( 5 ), a fifth multiplier ( 8 ), and a second time division multiplexer ( 12 ), which are connected in order; c) a seventh multiplier ( 6 ) and an eighth multiplier ( 9 ) connected in order; d) a pseudo-code generator ( 1 ) connected to the first multiplier ( 3 ), the fourth multiplier ( 2 ), and the seventh multiplier ( 6 ); e) a first frequency divider ( 17 ) connected to the pseudo-code generator ( 1 ); f) a subcarrier generator connected to the second multiplier ( 7 ), the fifth multiplier ( 8 ), and the eighth multiplier ( 9 ); and g) a second frequency divider ( 18 ) connected to the first time division multiplexer ( 11 ) and the second time division multiplexer ( 12 ); wherein the first multiplier ( 3 ) is connected to the second adder ( 5 ); the fourth multiplier ( 2 ) is connected to the first subtracter ( 4 ); the eighth multiplier ( 9 ) is connected to the second time division multiplexer ( 12 ); the first time division multiplexer ( 11 ) and second time division multiplexer ( 12 ) are connected to a RF modulator; and the first time division multiplexer ( 11 ) receives zero signal input.

4. A system for modulating navigation signal according the method of claim 2 , the system comprising: a frequency divider ( 24 ) and a pseudo-code generator ( 19 ); wherein the frequency divider ( 24 ) and the pseudo-code generator ( 19 ) are connected; the pseudo-code generator ( 19 ) is connected to a first input terminal of a baseband modulation module ( 26 ) through a first Exclusive-OR operator ( 20 ); the pseudo-code generator ( 19 ) is connected to a second input terminal of the baseband modulation module ( 26 ) through a second Exclusive-OR operator ( 21 ); the pseudo-code generator ( 19 ) is also connected to a third input terminal of the baseband modulation module ( 26 ); two output terminals of the baseband modulation module ( 26 ) are connected to a RF modulator.